Chlorination for low-cost household water disinfection - A critical review and status in three Latin American countries.

Chlorination has historically provided microbiologically safe drinking water in public water supplies. Likewise, chlorine has also been introduced as a low-cost disinfection method in rural and marginalized communities, both at community and household level, as well as during emergencies. Although this practice is common and well established for use as a household water treatment technology in the Global South, several challenges in effective and efficient implementation still need to be addressed. Here, we explored these issues by a literature review and narrowed them to the status of three Latin American countries (Mexico, Colombia, and Brazil). Overall, it was found that although guidance on household-based chlorination includes information on health risks and hygiene, this may not create enough incentive for the user to adapt the method satisfactorily. Physicochemical quality of the water influences chlorination efficiency and it is found that variations in quality are rarely considered when recommending chlorine doses during implementation. These are far more often based on a few measurements of turbidity, thereby not considering dissolved organic matter, or seasonal and day-to-day variations. Other factors such as user preferences, chlorine product quality and availability also represent potential barriers to the sustainable use of chlorination. For chlorination to become a sustainable household water treatment, more focus should therefore be given to local conditions prior to the intervention, as well as support and maintenance of behavioural changes during and after the intervention.

Dictionary-based software for proton dose reconstruction and submilimetric range verification.

Objective.This paper presents a new method for fast reconstruction (compatible with in-beam use) of deposited dose during proton therapy using data acquired from a PET scanner. The most innovative feature of this novel method is the production of noiseless reconstructed dose distributions from which proton range can be derived with high precision.Approach.A new MLEM & simulated annealing (MSA) algorithm, developed especially in this work, reconstructs the deposited dose distribution from a realistic pre-calculated activity-dose dictionary. This dictionary contains the contribution of each beam in the plan to the 3D activity and dose maps, as calculated by a Monte Carlo simulation. The MSA algorithm, usinga prioriinformation of the treatment plan, seeks for the linear combination of activities of the precomputed beams that best fits the observed PET data, obtaining at the same time the deposited dose.Main results.the method has been tested using simulated data to determine its performance under 4 different test cases: (1) dependency of range detection accuracy with delivered dose, (2) in-beam versus offline verification, (3) ability to detect anatomical changes and (4) reconstruction of a realistic spread-out Bragg peak. The results show the ability of the method to accurately reconstruct doses from PET data corresponding to 1 Gy irradiations, both in intra-fraction and inter-fraction verification scenarios. For this dose level (1 Gy) the method was able to spot range variations as small as 0.6 mm.Significance.out method is able to reconstruct dose maps with remarkable accuracy from clinically relevant dose levels down to 1 Gy. Furthermore, due to the noiseless nature of reconstructed dose maps, an accuracy better than one millimeter was obtained in proton range estimates. These features make of this method a realistic option for range verification in proton therapy.

Adaptación e implementación del modelo de prevención de consumo de sustancias Planet Youth en Chile / Adaptation and implementation of the Planet Youth substance use prevention model in Chile

Resumen El consumo de sustancias en adolescentes es altamente prevalente en varias regiones del mundo, y especialmente en Chile, siendo su prevención un importante desafío para la salud pública. Este artículo describe el modelo islandés de prevención del consumo de sustancias en adolescentes "Planet Youth", su adaptación y factibilidad de implementación en Chile, como primera experiencia en Latinoamérica. Este modelo comunitario está enfocado en la prevención ambiental y en la promoción de la salud de niños, niñas y adolescentes, basado en un diagnóstico local y oportuno de factores protectores y de riesgo, con colaboración de la autoridad local y la academia. Seis comunas de la región metropolitana en colaboración con la Universidad de Chile y el Icelandic Centre for Social Research and Analysis inician su implementación en 2018. Se tradujo y adaptó la encuesta islandesa que fue aplicada a 7354 estudiantes de 2° medio, cuyos resultados se retroalimentaron a colegios y municipalidades para trabajar en la modificación de los principales factores de riesgo y protección. En 2020, el proceso ha requerido algunas adaptaciones debido a la pandemia por COVID-19. Se discute acerca de factores socioculturales relevantes en la adaptación de estrategias basadas en evidencia internacional que se transfieren a un país diferente. La implementación del modelo Planet Youth es factible en Chile y ofrece una importante oportunidad para prevenir el consumo de sustancias en jóvenes de manera efectiva en Latinoamérica.

The prevalence of substance use is high among adolescents in several region around the world, specifically in Chile, and its prevention is an important public health challenge. We describe the adaptation and the feasibility to implement the Icelandic model of substance use prevention in adolescents "Planet Youth" in Chile as first experience in Latin America. This community prevention model focuses on the environment, culture and the promotion of health in adolescents, informed by local risk and protective factors. Implementation requires collaboration between academia and municipal authorities. Six municipalities of the Metropolitan Region, the University of Chile and the Icelandic Centre for Social Research and Analysis collaborated in the implementation of the Planet Youth model since 2018 in Chile. A substance use survey was translated, adapted, and applied to 7354 tenth grade students. The results were informed to schools and municipalities in order to work on modifications of the main risk and protective factors in their own community. In 2020, the prevention process has required some adaptation due to COVID-19 pandemic. We discuss sociocultural factors in the adaptation of this international prevention model transferred to Latin America. The implementation of the Planet Youth model is feasible in Chile and offers an opportunity to effectively prevent the substance use behaviors of adolescents in Latin America.

EMA-amplicon-based sequencing informs risk assessment analysis of water treatment systems.

Illumina amplicon-based sequencing was coupled with ethidium monoazide bromide (EMA) pre-treatment to monitor the total viable bacterial community and subsequently identify and prioritise the target organisms for the health risk assessment of the untreated rainwater and rainwater treated using large-volume batch solar reactor prototypes installed in an informal settlement and rural farming community. Taxonomic assignments indicated that Legionella and Pseudomonas were the most frequently detected genera containing opportunistic bacterial pathogens in the untreated and treated rainwater at both sites. Additionally, Mycobacterium, Clostridium sensu stricto and Escherichia/Shigella displayed high (≥80%) detection frequencies in the untreated and/or treated rainwater samples at one or both sites. Numerous exposure scenarios (e.g. drinking, cleaning) were subsequently investigated and the health risk of using untreated and solar reactor treated rainwater in developing countries was quantified based on the presence of L. pneumophila, P. aeruginosa and E. coli. The solar reactor prototypes were able to reduce the health risk associated with E. coli and P. aeruginosa to below the 1 × 10-4 annual benchmark limit for all the non-potable uses of rainwater within the target communities (exception of showering for E. coli). However, the risk associated with intentional drinking of untreated or treated rainwater exceeded the benchmark limit (E. coli and P. aeruginosa). Additionally, while the solar reactor treatment reduced the risk associated with garden hosing and showering based on the presence of L. pneumophila, the risk estimates for both activities still exceeded the annual benchmark limit. The large-volume batch solar reactor prototypes were thus able to reduce the risk posed by the target bacteria for non-potable activities rainwater is commonly used for in water scarce regions of sub-Saharan Africa. This study highlights the need to assess water treatment systems in field trials using QMRA.

Fast optimized Monte Carlo phase-space generation and dose prediction for low energy x-ray intra-operative radiation therapy.

Low energy x-ray intra-operative radiation therapy (IORT) is used mostly for breast cancer treatment with spherical applicators. X-ray IORT treatment delivered during surgery (ex: INTRABEAM®, Carl Zeiss) can benefit from accurate and fast dose prediction in a patient 3D volume. However, full Monte Carlo (MC) simulations are time-consuming and no commercial treatment planning system (TPS) was available for this treatment delivery technique. Therefore, the aim of this work is to develop a dose computation tool based on MC phase space information, which computes fast and accurate dose distributions for spherical and needle INTRABEAM® applicators. First, a database of monoenergetic phase-space (PHSP) files and depth dose profiles (DDPs) in water for each applicator is generated at factory and stored for on-site use. During commissioning of a given INTRABEAM® unit, the proposed fast and optimized phase-space (FOPS) generation process creates a phase-space at the exit of the applicator considered, by fitting the energy spectrum of the source to a combination of the monoenergetic precomputed phase-spaces, by means of a genetic algorithm, with simple experimental data of DDPs in water provided by the user. An in-house hybrid MC (HMC) algorithm which takes into account condensed history simulations of photoelectric, Rayleigh and Compton interactions for x-rays up to 1 MeV computes the dose from the optimized phase-space file. The whole process has been validated against radiochromic films in water as well as reference MC simulations performed with penEasy in heterogeneous phantoms. From the pre-computed monoenergetic PHSP files and DDPs, building the PHSP file optimized to a particular depth-dose curve in water only takes a few minutes in a single core (i7@2.5 GHz), for all the applicators considered in this work, and this needs to be done only when the x-ray source (XRS) is replaced. Once the phase-space file is ready, the HMC code is able to compute dose distributions within 10 min. For all the applicators, more than 95% of voxels from dose distributions computed with the FOPS+hybrid code agreed within 7%-0.5 mm with both reference MC simulations and measurements. The method proposed has been fully validated and it is now implemented into radiance (GMV SA, Spain), the first commercial IORT TPS.

Phase space determination from measured dose data for intraoperative electron radiation therapy.

A procedure to characterize beams of a medical linear accelerator for their use in Monte Carlo (MC) dose calculations for intraoperative electron radiation therapy (IOERT) is presented. The procedure relies on dose measurements in homogeneous media as input, avoiding the need for detailed simulations of the accelerator head. An iterative algorithm (EM-ML) has been employed to extract the relevant details of the phase space (PHSP) of the particles coming from the accelerator, such as energy spectra, spatial distribution and angle of emission of particles. The algorithm can use pre-computed dose volumes in water and/or air, so that the machine-specific tuning with actual data can be performed in a few minutes. To test the procedure, MC simulations of a linear accelerator with typical IOERT applicators and energies, have been performed and taken as reference. A solution PHSP derived from the dose produced by the simulated accelerator has been compared to the reference PHSP. Further, dose delivered by the simulated accelerator for setups not included in the fit of the PHSP were compared to the ones derived from the solution PHSP. The results show that it is possible to derive from dose measurements PHSP accurate for IOERT MC dose estimations.

[Assessment of educational performance of different teaching methodologies applied to medical students in the area of arterial hypertension]. / Evaluación del rendimiento educacional mediante la utilización de diferentes opciones metodológicas aplicadas a estudiantes de medicina, en el área de la hipertensión arterial.

BACKGROUND: Modernization of medical teaching includes the use of new teaching methodologies and among these, computer assisted tutorials. Previous experience has shown that this type of methodology is associated with better student performances. AIM: To assess the cognitive performance of fourth year medical students using different teaching methodologies. MATERIAL AND METHODS: During the hypertension course, medical students were allowed to choose to receive a printed booklet (group A), to receive the booklet and attend lectures (group B), to receive the booklet and use a multimedial educational program (group C) and to use all three methodologies (group D). Cognitive performance was evaluated with a multiple choice test scored from 0 to 100. RESULTS: The mean scores obtained by students were 84.5 in group A, 82.4 in group B, 88.9 in group C and 84.4 in group D. This overall score of 83.6 in hypertension was significantly better than the mean score of 72.5 obtained in the cardiology test. CONCLUSIONS: Allowing students to choose the most suitable method to learn according to their personal preferences, results in a better cognitive performance.

[Assessment of the feasibility of a distance medical education program]. / Evaluación de la aplicabilidad de un programa de educación médica a distancia.

BACKGROUND: Continuing medical education is essential to cope with the accelerated evolution of medical knowledge. AIM: To assess the feasibility of a distance medical education program prepared in a written format. SUBJECTS AND METHODS: Ninety physicians, aged 25 to 29 years old and with 1 to 4 years of medical practice, working mostly in rural locations, participated in the program. The sending of 10 issues with medical topics was programmed. The topics were selected according to the results of an survey done among physicians of the region. Each issue contained an evaluation that had to be returned to the authors. RESULTS: Eighty two physicians completed the program and 59 returned the evaluations. The mean obtained score in the cognitive evaluation was 80 +/- 6 points (range 68 to 97 points) of a scale from 0 to 100. The qualitative survey revealed a high degree of approval of the issue's format, contents and evaluation system. The favorable effect on patient's management and on the detection and control of chronic diseases was emphasized. CONCLUSIONS: This distance medical education program had a good receipt and compliance among physicians and contributed to continuing medical training.

Caffeine test assessment for measuring liver function in critically ill patients.

Caffeine elimination was studied in 73 patients admitted to an intensive care unit, 33 of whom had liver disease. Mean plasma clearance of caffeine in patients with no liver disease (1.30 +/- 0.79 ml/kg/min) was significantly higher than in patients with liver disease (0.39 +/- 0.23 ml/kg/min). Mean half-life of caffeine in patients with liver disease (23.96 +/- 12.19 h) was significantly higher than in patients with no liver disease (7.25 +/- 3.04 h). No significant differences in distribution volumes were found. Receptor-operator curves (ROC) for plasma clearance and the half-life of elimination of caffeine showed a high diagnostic value. Therefore, the parameters for caffeine biotransformation, i.e. Cl and t1/2, are useful for assessing liver function in the population studied.